Additive Free Co-Lean Ternary NiCoAl/Ni Foam Electrode for High-Efficiency Energy Storage and Low-Grade Heat Harvesting

Abstract

This work aims to develop a sustainable, additive-free, and Co-lean ternary NiCoAl layered double hydroxide (NCA) electrode capable of delivering high-performance electrochemical energy storage and low-grade heat harvesting. A Ni-rich, Co-lean NCA was directly grown on nickel foam (NCA/NF) via a simple hydrothermal process, forming 3D hierarchical microflowers composed of ultrathin (27 nm) nanosheets. The optimized Ni:Co:Al ratio (4:2:1) maximizes Ni²⁺/Ni³⁺ redox activity, stabilizes the LDH lattice through Al³⁺ incorporation, and enhances charge-transfer kinetics via Ni-O-Co interactions. The resulting NCA/NF electrode delivers a specific capacitance of 3346 F g-1 (5019 mF cm-2) at 1.5 A g-1 and enables an asymmetric supercapacitor with a specific energy of 55.4 Wh kg-1 at 797.7 W kg-1, retaining 51.1 Wh kg-1 even at 7998.2 W kg-1. Combined with 92% capacity retention over 25,000 cycles, the NCA/NF electrode simultaneously retains specific energy and power capability. This well-balanced energy-power-stability performance is a critical requirement for next-generation high-power electrochemical systems and is rarely achieved in fully additive-free LDH electrodes. In parallel, the NCA/NF electrode functions as an efficient thermoelectrochemical material, achieving a Seebeck coefficient of 5.5 mV K-1 and storing 1.65 J of thermal charge under a modest 0-10 K gradient. This performance has not previously been reported for Ni-based electrodes at such low ΔT. These findings establish Ni-rich, Co-lean NCA/NF as a scalable and sustainable bifunctional electrode platform that unites compositional tuning, structural integrity, and efficient energy storage and conversion capability.

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